A typical passenger conveyor, such as an escalator or moving walk, includes a frame, balustrades with movable handrails, steps, and a drive system and a step chain for propelling the steps. The frame includes a truss section on both left and right hand sides of the frame. Each truss section has two end sections forming landings, which are connected by an inclined midsection. The upper landing usually houses the escalator drive system or machine positioned between the trusses.
The drive system of the escalator typically consists of a step chain, a step chain drive sprocket, an axle and a drive motor. The drive motor drives the step chain to travel in a continuous closed loop.
As shown in FIGS. 1 and 2, steps 10, which are attached to a step chain 12, run from one landing to the other in order to transport the passengers.
Support levers 16 are fixedly coupled to both sides of the step 10. Each support lever 16 is provided with a step roller 18, which is rotatably mounted to an end of the support lever 16. The step roller 18 guides the movement of the step 10 and supports the same.
An escalator has a track 20 on both left and right sides, along which the step roller 18 travels in a continuous closed loop. The track 20 is substantially parabolic in shape at the turn around areas located under the lower landing and the upper landing. This is so that the step roller 18 and the step 10 can make a 180 degree heading change at the turn around areas.
The track 20 includes an inner rail 22 and an outer rail 24 that is disposed outward of the inner rail 22. The gap between the inner rail 22 and the outer rail 24 is set to be larger than the diameter of the step roller 18 by about 2 mm to 3 mm.
At the passenger conveying area, the step roller 18 rolls on the inner rail 22 of the track 20. Since the step 10 moves upward, the step roller 18 rises from the inner rail 22 to the outer rail 24 when the step roller 18 advances into the curved portion of the track 20 at the upper turn around area. This is due to the inertia of the moving step 10. Thus, the step roller 18 tends to collide with the outer rail 24. Then, the step roller 18 descends toward the lower landing with rolling on the outer rail 24 and returns onto the inner rail 22 at the lower turn around area.
However, the collisions of the step roller 18 with the rails 22 and 24 of the track 20 cause noise and operational instability, thus making the passengers feel very uncomfortable. Such collisions may even lead to the malfunction of the escalator.
To solve this problem, as shown in FIG. 3, a prior art shock absorbing device for an escalator consists of leaf springs 22a and 24a, which are formed at the inner rail 22 and the outer rail 24 of the track 20, respectively. The leaf springs 22a and 24a serve as shock-absorbing means. The step roller 18 advancing into the upper curved portion of the track 20 bounces from the leaf spring 22a of the inner rail 22 and collides with the outer rail 24. The leaf spring 24a of the outer rail 24 vibrates in order to absorb shock and reduce noise.
However, the above prior art shock absorbing device for an escalator requires troublesome calculation of spring constants and high precision of a gap between the inner rail and the outer rail. This is so that the leaf springs may sufficiently absorb the shocks resulting from the collisions of the step roller. Further, since the leaf springs tend to get deformed by repeated collisions with the step roller, frequent repairs are required.